Watercraft have remained largely unchanged for thousands of years, generally utilizing a displacement member with a fixed volume and rigid exterior and generally obtaining propulsion from sails, oars, or, more recently, paddle wheels, propellers, impellers, or air fans. Recent developments include the “trampfoil” and a flipper-craft, by Hobbiecraft, Inc., which is the subject of U.S. Pat. No. 6,022,249. A schematic drawing of the trampfoil, prepared from publicly available color drawings, is provided in FIG. 1.A. The trampfoil utilizes two underwater wings or hydrofoils 1.A.01 and 1.A.02 to generate forward thrust and lift, force being provided by the vertical translation of the user who stands on the platform 1.A.03. While fast for a human powered craft (it planes and can travel at around 20 mph), if the craft stops, it sinks. Neither the wings nor the platform 1.A.03 provide sufficient displacement to support the weight of the user.
Two schematic drawings of the PumpaBike, prepared from publicly available color drawings, are provided in FIG. 1.B. The PumpaBike, a version of the trampfoil, has been developed which includes a displacement body 1.B.04 to displace water and provide floatation for the user when the user is not providing power. The displacement body is lifted from the water when the PumpaBike is in motion and exceeds a minimum speed (as shown in FIG. 1.B). The PumpaBike includes a spring between the displacement body and the supports 1.B.08 for the hydrofoils 1.B.01 and 1.B.02, which spring is probably compressed by some portion of the downward cycle in the user's vertical translation and which spring probably releases its stored energy around the beginning of the upward cycle of the user's vertical translation. The uncompressed spring is represented in FIG. 1.B by element 1.B.06. The PumpaBike is otherwise similar to the trampfoil. The Pumpabike can float, but, like the trampfoil, it cannot be started from the water. In addition, and as with the trampfoil, the operator must expend a significant amount of energy to maintain a planing state.
A drawing of the Hobbiecraft flipper-craft from U.S. Pat. No. 6,022,249 is provided in FIG. 1.C. The wings on the Hobbiecraft flipper-craft are attached to a more-or-less conventional boat body, which boat body provides flotation for the craft's payload. The wings on the Hobbiecraft flipper-craft are designed to produce thrust, not lift for the craft.
Required is a watercraft which provides sufficient flotation to support its payload, which provides an efficient mechanism for generating thrust and potentially lift, which does not require planing, and which utilizes a minimum of moving parts. Unlike many of the examples from the prior art discussed above, the presently disclosed craft is not designed to plane.